MP7 Regen issues

[OJ Avery]

I have a 12 granite with a mp7(us10 emissions). its been in a couple times now. Has had most of the emissions components replaced. the code that keeps reoccurring is an active code for ambient air temp sensor. the sensor and pigtail have been replaced. The sensor reads correct temp in ptt. The other problem that has been on going is that its calling for a regen often. the last completed regen shows about 50 hours ago. soot level is at 130% dpf, 7th inj, egr, dpf, boost pressure/temp sensor, pre/post nox sensor have been replaced, and the ecm reflashed.... Last time in I did a def piss test and it was good. January it was having the same regen often issue.

[turckster]

Injectors or turbo? Perform a snap test- remove exh. flex pipe before the dpf. With the engine at an idle have someone punch the throttle to max, there should be some soot right away but it should clear away within a few seconds. A slight haze is ok but for the most part it should be clear, if it smokes continuously then you may have an injector issue. Check intake system for leaks.  During a regen the boost psi should be under 10 psi for engines with out a recirculation valve, with the recirculation valve it will be slightly lower. If boost psi is too high remove the sra and verify the turbo sector shaft sweep. It should be smooth and feel a solid stop both ways(there is a tool for verifying full sweep). Any type of binding and the turbo is bad. 

Note: if you don't have PTT2 do not remove the sra, it must be calibrated before re-assembly 

[OJ Avery]

ok thanks turckster, I understand possible injector issue with the regen often, even though it runs good, I have run into that before. what about the ambient air temp code? It goes active often. the sensor and updated pigtail have been replaced. I checked for continuity from the connector at the sensor all the way to the dash. I have continuity at the dash but its pretty high resistance, 114 k ohm. what am I missing with that? and the 2 wouldn't be related correct?

[OJ Avery]

turckster, the ground circuit has 18 ohm resistance

[turckster]

As far as I know the Ambient temp sensor would not cause frequent regens. You should have 12v at pin #2 on the sensor. From pin #1 at the sensor to the instrument cluster pin 9B it should be anywhere from 0-10 ohms.  The FMI of the fault really determines how to diagnose the fault, without that you are guessing on what is wrong. The PDF is the wire diagram of the ambient temp sensor and related circuits. 

Untitled Document.pdf

[OJ Avery]

turckster, on the ambient air temp, I started checking resistance from sensor to bulkhead connector at firewall. at pin 1 I have .6 ohm. on the other pin I get a reading of 5 ohm and another pin in the block of 46 ohms. that tells me I've got a wiring issue.  

[OJ Avery]

Soooo, been awhile. That unit did end up needing injectors. I did a power balance test and it showed cyl 1 and 4 being off. so when I pulled injectors 3 and 6 were really carboned . as far as the ambient air temp I found the wiring to be ok. we've experienced in the past weird issues with our Verizon gps unit that hooks right into our diagnostic port, so I unplugged that for now.